//获取登录注册按钮区域，和注册后用户头像区域
let logarea = document.querySelector("header .log");
let userarea = document.querySelector("header .user");
let username = document.querySelector("header .user span");
let userhead = document.querySelector("header .user a");
let storage = window.sessionStorage;
// storage.setItem("u_name","我是某某用户");
let str = storage.getItem("u_name");
if(str){
  logarea.style.display = "none";
  username.innerText = str;
  userarea.style.display = "block";
};